U.S. patent application number 12/110461 was filed with the patent office on 2008-09-25 for optical element and method for manufacturing the same.
Invention is credited to Runa NAKAMURA, Keiko TAZAKI.
Application Number | 20080230933 12/110461 |
Document ID | / |
Family ID | 36611936 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080230933 |
Kind Code |
A1 |
TAZAKI; Keiko ; et
al. |
September 25, 2008 |
OPTICAL ELEMENT AND METHOD FOR MANUFACTURING THE SAME
Abstract
The present invention provides an optical element capable of
improving the adhesive property between a refractive index
anisotropic layer and an alignment property providing layer for.
providing alignment property to the refractive index anisotropic
layer and further improving the endurance of each of the layers. An
optical element 10 has an alignment property providing layer 12
laminated on a transparent base material 11 and a refractive index
anisotropic layer 13 laminated on the layer 12. The layer 12 is an
alignment layer having alignment limiting force for providing
alignment property to the layer 13, and is made of an alignment
layer composition capable of expressing the alignment limiting
force. The layer 13 is a liquid crystal layer formed by curing
(polymerizing) a liquid crystal composition comprising a
polymerizable liquid crystal material. A monomer or oligomer having
one or more functional groups, together with a polymer, is
incorporated into the alignment layer composition. The monomer or
oligomer in the layer 12 is crosslinked with molecules in the layer
13, which is adjacent to the layer 12, near the interface between
the layers 12 and 13.
Inventors: |
TAZAKI; Keiko; (Tokyo,
JP) ; NAKAMURA; Runa; (Tokyo, JP) |
Correspondence
Address: |
LADAS & PARRY LLP
224 SOUTH MICHIGAN AVENUE, SUITE 1600
CHICAGO
IL
60604
US
|
Family ID: |
36611936 |
Appl. No.: |
12/110461 |
Filed: |
April 28, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11315972 |
Dec 22, 2005 |
|
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12110461 |
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Current U.S.
Class: |
264/1.31 ;
264/1.7 |
Current CPC
Class: |
C09K 19/2007 20130101;
C09K 2019/0448 20130101; Y10T 428/1005 20150115; C09K 2219/03
20130101; G02B 5/3016 20130101; C09K 2323/021 20200801; Y10T
428/1009 20150115; C09K 19/322 20130101; C09K 2323/02 20200801;
C09K 2323/00 20200801; Y10T 428/10 20150115 |
Class at
Publication: |
264/1.31 ;
264/1.7 |
International
Class: |
B29D 11/00 20060101
B29D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2004 |
JP |
2004-381066 |
Aug 22, 2005 |
JP |
2005-239863 |
Claims
1. A method for manufacturing an optical element, comprising: a
step of forming an alignment property providing layer as an
alignment layer on a transparent base material, in which an
alignment layer composition comprising a polymer and a monomer or
an oligomer having one or more functional groups is applied onto
the transparent base material to express an alignment limiting
force on a surface thereof; a step of applying a liquid crystal
composition comprising a polymerizable liquid crystal material onto
the alignment property providing layer formed on the transparent
base material, and a step of forming a refractive index anisotropic
layer, in which the liquid crystal composition applied onto the
alignment property providing layer on the transparent base material
is cured to provide an alignment property to the alignment property
providing layer by the alignment limiting force of the alignment
property providing layer; wherein in the step of forming the
refractive index anisotropic layer, the alignment property
providing layer together with the liquid crystal composition is
cured to crosslink the monomer or the oligomer in the alignment
property providing layer and the polymerizable liquid crystal
material in the refractive index anisotropic layer with each other
near an interface between the alignment property providing layer
and the refractive index anisotropic layer.
2. The method for manufacturing the optical element according to
claim 1, wherein the alignment property providing layer formed on
the transparent base material is made of an alignment layer
composition capable of expressing the alignment limiting force by a
photo alignment method.
3. The method for manufacturing the optical element according to
claim 2, wherein the polymer comprised in the alignment layer
composition for forming the alignment property providing layer is
the polymer having at least one of a cinnamate and a coumalin.
4. The method for manufacturing the optical element according to
claim 1, wherein themonomer or the oligomer comprised in the
alignment layer composition for forming the alignment property
providing layer is the polymerizable liquid crystal material.
5. The method for manufacturing the optical element according to
claim 4, wherein the polymerizable liquid crystal material in the
alignment property providing layer and the polymerizable liquid
crystal material in the refractive index anisotropic layer are of a
same kind.
6. The method for manufacturing the optical element according to
claim 1, wherein a weight of the monomer or the oligomer comprised
in the alignment layer composition for forming the alignment
property providing layer is from 0.01 to 3 times that of the
polymer.
7. The method for manufacturing the optical element according to
claim 1, wherein a weight of the monomer or the oligomer comprised
in the alignment layer composition for forming the alignment
property providing layer is from 0.05 to 1.5 times that of the
polymer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical element such as
a retardation plate, a polarizing plate, or a color filter for
display, in particular, an optical element comprising, as a
refractive index anisotropic layer, a liquid crystal layer
comprising a liquid crystal composition containing a polymerizable
liquid crystal material; and a method for manufacturing the same.
In the specification and the claims, the term "liquid crystal
layer" means a layer having an optical liquid crystal property, and
the state of the layer may be a solid phase state that the
molecular arrangement which a liquid crystal phase has is kept and
solidified.
[0003] 2. Description of the Related Art
[0004] In general, liquid crystal is used as a display medium,
typical examples of which include TN (twisted nematic) and STN
(super twisted nematic) type display elements, by use of reversible
mobility of the molecular arrangement thereof. Besides, liquid
crystal is used as an optical element, such as a retardation plate,
a polarizing plate or a color filter for display, by use of the
alignment and the refractive index anisotropy thereof.
[0005] In connection with the latter usage, in recent years, there
have been proposed many optical elements which each has, as a
refractive index anisotropic layer, a liquid crystal layer made of
a polymerizable liquid crystal material. Specifically, for example,
Japanese Patent Application National Publication No. 2002-533742
describes an optical element having functions of
wavelength-selective reflectivity and polarization-selective
reflectivity and is produced by use of a special polymerizable
liquid crystal compound. Japanese Patent Application Laid-Open
(JP-A) No. 5-215921 describes a birefringent plate produced by use
of a polymerizable liquid crystal compound having a bar-like
structure. Furthermore, JP-A Nos. 8-338913 and 9-152509 each
describes an optical compensation sheet produced by use of a
polymerizable liquid crystal compound having a disc-like
structure.
[0006] Incidentally, as such an optical element, there is generally
used an optical element in which a liquid crystal layer (a
refractive index anisotropic layer) made of a polymerizable liquid
crystal material is laminated over a support, such as a plastic
film, so as to interpose an alignment layer therebetween.
[0007] The alignment layer arranged between the support and the
refractive index anisotropic layer has alignment limiting force for
limiting the alignment direction of liquid crystal molecules in the
refractive index anisotropic layer. Such an alignment layer can be
formed by forming a layer of a polymer (such as polyimide,
polyvinyl alcohol, or gelatin) having alignment property onto a
support, and then subjecting the polymer layer to alignment process
such as rubbing treatment. When rubbing treatment is applied, as
alignment process, to an alignment layer, static electricity or
dust is generated in or on the surface of this layer; accordingly,
methods have been researched for causing an alignment layer to
express alignment limiting force without conducting rubbing
treatment. One of them is a photo alignment method in which light
in an arbitrary polarized light state (polarized light) is radiated
onto an alignment layer, thereby generating alignment limiting
force (anisotropy) on the surface of the alignment layer. The photo
alignment method is classified into "photo isomerization", in which
only the shape of molecules is changed to vary the alignment state
thereof reversibly, and "photo reaction", in which molecules
themselves are changed. The "photo reaction" of the latter is
further classified into dimerization, decomposition, coupling,
decomposition-coupling, and others.
[0008] About the above-mentioned optical element, which comprises a
support, an alignment layer and a refractive index anisotropic
layer, it is undoubtedly important that the optical property of
each layer of the optical element is good. Besides, it is also
important that the adhesive property between the layers of the
optical element or the endurance of each of the layers is good. In
connection with the latter subject, for example, if the adhesive
property between an alignment layer and a refractive index
anisotropic layer which constitute an optical element is poor,
there arises a problem that the refractive index anisotropic layer
is easily peeled from the alignment layer. When the optical element
is used or stored at high temperature and high humidity, there also
arises a problem that netlike shriverings are generated in the
refractive index anisotropic layer.
[0009] In order to solve such problems, methods described below
have been proposed hitherto.
[0010] JP-A No. 9-152509 proposes a method of using a modified
polyvinyl alcohol as the material of an alignment layer and
improving the adhesive property between the alignment layer and a
refractive index anisotropic layer by chemical bond in the
interface between the two layers. JP-A No. 10-10320 proposes a
method of inserting an anchor coat layer between layers having a
low adhesive property with each other, thereby improving the
adhesive property between these layers. Furthermore, Japanese
Patent Application National Publication No. 2000-514202 proposes a
method of adding a monomer into a material for a refractive index
anisotropic layer, thereby improving the endurance of the
refractive index anisotropic layer. Specifically, there is proposed
a method of incorporating, into a reactive mesogen compound as a
material for a refractive index anisotropic layer, a non-mesogen
compound having 2 or more polymerizable functional groups in an
amount of 20% or less of the mesogen compound, thereby changing the
glass transition temperature, the thermal stability and the
mechanical stability of the layer.
[0011] Of the above-mentioned methods in the prior art, however,
the method described in JP-A No. 9-152509 has the following
problem: the boiling point of a solvent used for the modifying
reaction of the polyvinyl alcohol is high and a solution containing
this solvent cannot be used, as it is, as a coating solution;
accordingly, a step of purifying the polyvinyl alcohol by the
re-precipitation thereof is indispensable, so that costs for the
production increase. The method described in JP-A No. 10-10320 has
a problem that when a liquid crystal compound is used as the
material of the refractive index anisotropic layer, the liquid
crystal molecules are not satisfactorily aligned on the anchor coat
layer. The method described in the Japanese Patent Application
National Publication No. 2000-514202 has the following problem:
when the alignment state of the liquid crystal molecules is fixed
after the alignment process thereof so as to make the liquid
crystal into a refractive index anisotropic layer, additives become
impurities when the liquid crystal molecules are aligned; thus, the
alignment of the liquid crystal molecules is hindered, so that the
optical property thereof lowers (for example, display unevenness is
generated.)
SUMMARY OF THE INVENTION
[0012] The present invention has been made in light of such a
situation. An object thereof is to provide an optical element
wherein a liquid crystal layer comprising a liquid crystal
composition containing a polymerizable liquid crystal material is
used as a refractive index anisotropic layer, the optical element
being capable of heightening the adhesive property between the
refractive index anisotropic layer and an alignment property
providing layer for providing alignment property to the refractive
index anisotropic layer, and further improving the endurance of
each of the layers; and a method for manufacturing the same.
[0013] As first resolving means, the present invention provides an
optical element comprising a transparent base material, an
alignment property providing layer laminated on the transparent
base material, and a refractive index anisotropic layer laminated
on the alignment property providing layer and having an alignment
property provided by alignment limiting force of the alignment
property providing layer, wherein the alignment property providing
layer is made of alignment layer comprising an alignment layer
composition capable of expressing the alignment limiting force, the
alignment layer composition comprises a polymer and a monomer or
oligomer having one or more functional groups, wherein the
refractive index anisotropic layer is made of a liquid crystal
layer formed by curing a liquid crystal composition comprising a
polymerizable liquid crystal material, and in the alignment
property providing layer and the refractive index anisotropic
layer, the monomer or oligomer in the alignment property providing
layer and the polymerizable liquid crystal material in the
refractive index anisotropic layer are crosslinked with each other
near an interface between the layers.
[0014] According to the first resolving means, it is preferred that
the alignment property providing layer is an alignment layer
comprising the alignment layer composition capable of expressing
the alignment limiting force by a photo alignment method. It is
preferred that the polymer comprised in the alignment layer
composition for forming the alignment property providing layer is a
polymer having at least one of cinnamate and coumalin.
[0015] According to the first resolving means, it is also preferred
that the monomer or oligomer comprised in the alignment layer
composition for forming the alignment property providing layer is
isocyanuric acid (meth)acrylate.
[0016] According to the first resolving means, it is also preferred
that the monomer or oligomer comprised in the alignment layer
composition for forming the alignment property providing layer is a
polymerizable liquid crystal material. It is preferred that the
polymerizable liquid crystal material in the alignment property
providing layer and the polymerizable liquid crystal material in
the refractive index anisotropic layer are of the same kind.
[0017] According to the first resolving means, the weight of the
monomer or oligomer comprised in the alignment layer composition
for forming the alignment property providing layer is preferably
from 0.01 to 3 times that of the polymer, more preferably from 0.05
to 1.5 times that of the polymer.
[0018] As second resolving means, the present invention provides a
method for manufacturing an optical element, comprising: a step of
forming an alignment property providing layer as an alignment layer
on a transparent base material, in which an alignment layer
composition comprising a polymer and a monomer or an oligomer
having one or more functional groups is applied onto the
transparent base material to express an alignment limiting force on
a surface thereof; a step of applying a liquid crystal composition
comprising a polymerizable liquid crystal material onto the
alignment property providing layer formed on the transparent base
material, and a step of forming a refractive index anisotropic
layer, in which the liquid crystal composition applied onto the
alignment property providing layer on the transparent base material
is cured to provide an alignment property to the alignment property
providing layer by the alignment limiting force of the alignment
property providing layer; wherein in the step of forming the
refractive index anisotropic layer, the alignment property
providing layer together with the liquid crystal composition is
cured to crosslink the monomer or the oligomer in the alignment
property providing layer and the polymerizable liquid crystal
material in the refractive index anisotropic layer with each other
near an interface between the alignment property providing layer
and the refractive index anisotropic layer. The "functional
group(s)" that the monomer or oligomer has is one or more groups
which can react with the polymerizable group that the polymerizable
liquid crystal material has.
[0019] According to the second resolving means, it is preferred
that the alignment property providing layer formed on the
transparent base material is made of the alignment layer
composition capable of expressing the alignment limiting force by a
photo alignment method. It is preferred that the polymer comprised
in the alignment layer composition for forming the alignment
property providing layer is a polymer having at least one of
cinnamate and coumalin.
[0020] According to the second resolving means, it is also
preferred that the monomer or oligomer comprised in the alignment
layer composition for forming the alignment property providing
layer is a polymerizable liquid crystal material. It is preferred
that the polymerizable liquid crystal material in the alignment
property providing layer and the polymerizable liquid crystal
material-in the refractive index anisotropic layer are of the same
kind.
[0021] According to the second resolving means, the weight of the
monomer or oligomer comprised in the alignment layer composition
for forming the alignment property providing layer is preferably
from 0.01 to 3 times that of the polymer, more preferably from 0.05
to 1.5 times that of the polymer.
[0022] As third resolving means, the present invention provides an
alignment layer composition for forming an alignment layer for
providing alignment property to a liquid crystal layer formed by
curing a liquid crystal composition comprising a polymerizable
liquid crystal material, comprising a polymer, and a monomer or
oligomer having one or more functional groups, wherein the monomer
or oligomer is capable of being crosslinked with the polymerizable
liquid crystal material in the liquid crystal layer.
[0023] According to the third resolving means, the polymer is
preferably a polymer having at least one of cinnamate and
coumalin.
[0024] According to the third resolving means, the monomer or
oligomer is preferably a polymerizable liquid crystal material.
[0025] According to the third resolving means, the weight of the
monomer or oligomer is preferably from 0.01 to 3 times that of the
polymer, more preferably from 0.05 to 1.5 times that of the
polymer.
[0026] According to the present invention, a monomer or oligomer
having one or more functional groups is added to an alignment layer
composition for forming an alignment property providing layer for
providing alignment property to a refractive index anisotropic
layer, whereby the monomer or oligomer in the alignment property
providing layer is crosslinked with molecules in the refractive
index anisotropic layer adjacent to the alignment property
providing layer near an interface between the alignment property
providing layer and the refractive index anisotropic layer. It is,
therefore, possible to improve the adhesive property between the
alignment property providing layer and there fractive index
anisotropic layer. A monomer or oligomer having two or more
functional groups is added to the above-mentioned alignment layer
composition, whereby the structure of the alignment property
providing layer made of the alignment layer composition becomes a
strong network structure. It is therefore possible to improve the
strength of the alignment property providing layer itself. In this
way, the finally-produced optical element becomes an optical
element excellent in the adhesive property between the alignment
property providing layer and the refractive index anisotropic layer
and in the endurance of each of the layers. It is consequently
possible to solve effectively problems that the refractive index
anisotropic layer is peeled and further a rise in the haze and the
appearance of unevenness are caused on the basis of poor alignment,
and other problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a sectional view schematically showing an optical
element according to an embodiment of the present invention.
[0028] FIG. 2 is a sectional view schematically showing a modified
example of the optical element shown in FIG. 1.
[0029] FIG. 3 is a sectional view schematically showing another
modified-example of the optical element shown in FIG. 1.
[0030] FIG. 4 is a sectional view schematically showing a further
modified example of the optical element shown in FIG. 1.
[0031] FIG. 5 is a sectional view schematically showing an even
further modified example of the optical element shown in FIG.
[0032] FIGS. 6A to 6G are process charts for explaining a
manufacturing method of an optical element according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Embodiments of the present invention will be described with
reference to the drawings.
[0034] First, the structure of an optical element according to an
embodiment of the invention is described with reference to FIG.
1.
[0035] As shown in FIG. 1, the optical element according to the
present embodiment is an optical element 10 having a transparent
base material 11, an alignment property providing layer 12
laminated on the transparent base material 11, and a refractive
index anisotropic layer 13 laminated on the alignment property
providing layer 12.
[0036] Of these members, the transparent base material 11 is a
support for supporting the alignment property providing layer 12
and the refractive index anisotropic layer 13, and is made of
glass, a transparent resin film, or the like. The transparent resin
film may be a film made of a cellulose resin such as
triacetylcellulose (TAC), diacetylcellulose or acetate butyrate
cellulose, a polyester resin such as polyethylene terephthalate
(PET) or polyester, an olefin resin such as polyethylene,
polyacrylic resin, polyurethane resin, polyethersulfone,
polycarbonate, polysulfone, polyether, polymethylpentene,
polyetherketone, (meth)acrylonitrile, or the like. As the
transparent resin film, a film made of triacetate cellulose (TAC)
having no birefringence is preferably used.
[0037] The transparent base material 11 preferably has a thickness
of about 25 to 1000 .mu.m. The transparent base material 11 may be
a continuous long film having a provided length, more specifically,
a continuous film which is in general industrially used and is
supplied in a roll-wounded form. The length of the long film can be
selected at will. When the film is in a roll-wounded form, the
length thereof can be set to, for example, a large length of
approximately 10000 m.
[0038] The alignment property providing layer 12 is an alignment
layer having alignment limiting force for providing alignment
property to the refractive index anisotropic layer 13, and is made
of an alignment layer composition capable of expressing the
alignment limiting force. The thickness of the alignment property
providing layer 12 is preferably from about 0.01 to 0.5 .mu.m.
[0039] For the alignment layer composition for forming the
alignment property providing layer 12, a polymer, a coupling agent
and so on may be used. Specific examples of the polymer include
polymethyl methacrylate, acrylic acid-methacrylic acid copolymer,
styrene-maleimide copolymer, polyvinyl alcohol, modified polyvinyl
alcohol, gelatin, styrene-vinyl toluene copolymer, chlorosulfonated
polyethylene, nitrocellulose, polyvinyl chloride, chlorinated
polyolefine, polyester, polyimide, vinyl acetate-vinyl chloride
copolymer, ethylene-vinyl acetate copolymer,
carboxymethylcellulose, polyethylene, polypropylene, and
polycarbonate. An example of the coupling agent is a silane
coupling agent.
[0040] The method for causing the alignment property providing
layer 12, which is made of such an alignment layer composition, to
express alignment limiting force may be a method of subjecting the
alignment property providing layer 12 to alignment process such as
rubbing treatment, or a method of using a photo alignment method to
subject the layer to alignment process. The photo alignment method
is a method of radiating light in an arbitrary polarized light
state (polarized light) onto an alignment layer, thereby expressing
alignment limiting force (anisotropy) onto the surface of the
alignment layer. As described above, the photo alignment method is
classified into "photo isomerization", in which only the shape of
molecules is changed to vary the alignment state thereof
reversibly, and "photo reaction", in which molecules themselves are
changed. The "photo reaction" of the latter is further classified
into dimerization, decomposition, coupling, decomposition-coupling,
and others. Of these, the method for the "dimerization", which is
generally used as the photo alignment method, is described as an
example. According to this method, light in an arbitrary polarized
light state (polarized light) is radiated onto an alignment layer,
whereby a chemical reaction such as dimerization reaction is caused
in the polarization direction thereof on the surface of the
alignment layer, so as to express alignment limiting force. A
typical example of the polymer which expresses alignment limiting
force by such "dimerization" is polyvinyl cinnamate (PVCi). In
polyvinyl cinnamate (PVCi), for example, radiation of polarized
ultraviolet rays causes double bond moieties of two side chains
parallel to the polarized rays to be opened by dimerization
reaction, and then the bonds are recoupled with each other. Other
preferred examples of the polymer which expresses alignment
limiting force by such "dimerization" include polymers having a
cinnamoyl group, a coumalin group, or a chalcone group (see, for
example, JP-A Nos. 7-138380 and 10-324690). Examples of the polymer
which expresses alignment limiting force by the above-mentioned
"dimerization" include polymers having cinnamate, coumalin,
benzilidenephthalimidine, benzilideneacetophenone,
diphenylacetylene, stylbazole, uracil, quinolinone, maleimide, or a
cinnamilidene acetic acid derivative. Of these, polymers having
cinnamate or coumalin, and polymers having cinnamate and coumalin
are preferred in the present invention (see, for example, JP-A No.
9-118717, and Japanese Patent Application National Publication Nos.
10-506420 and 2003-505561).
[0041] The cinnamate and coumalin used in the present invention are
preferably represented by the following formulae Ia and Ib:
##STR00001##
[0042] wherein A represents pyrimidine-2,5-diyl, pyridine-2,5-diyl,
2,5-thiophenylene, 2,5-furanylene, or 1,4- or 1,6-naphthylene, or
represents unsubstituted phenylene, or phenylene mono- or
multi-substituted with one or more fluorine atoms, chlorine atoms,
or cyclic, linear or branched alkyl residues which each have 1 to
18 carbon atoms (and which are each unsubstituted, or mono- or
multi-substituted with one or more fluorine atoms or chlorine
atoms, one or more out of their --CH.sub.2-- groups which are not
adjacent to each other being allowed to be independently
substituted with a group C [wherein C represents a group selected
from --O--, --CO--, --CO--O--, --O--CO--, --NR.sup.1--,
--NR.sup.1--CO--, --CO--NR.sup.1--, --NR.sup.1--CO--O--,
--O--CO--NR.sup.1--, --NR.sup.1--CO--NR.sup.1--, --CH.dbd.CH--,
--C.ident.C--, --O--CO--O-- and
-Si(CH.sub.3).sub.2--O-Si(CH.sub.3).sub.2-- wherein R.sup.1
represents a hydrogen atom or a lower alkyl]);
[0043] B represents a hydrogen atom, or a group capable of reacting
or interacting with a second material (such as a polymer, an
oligomer, a monomer, an photoactive polymer, an photoactive
oligomer, and/or an photoactive monomer), or a surface;
[0044] S.sub.1 and S.sub.2 each independently represent a single
bond or a spacer unit, such as a linear or branched alkylene group
having 1 to 40 carbon atoms (and is unsubstituted, or mono- or
multi-substituted with one or more fluorine or chlorine atoms, one
or more out of its --CH.sub.2-- groups which are not adjacent to
each other being allowed to be independently substituted with a
group D [wherein D represents a group selected from --O--, --CO--,
--CO--O--, --O--CO--, --NR.sup.1--, --NR.sup.1--CO--,
--CO--NR.sup.1--, --NR.sup.1--CO--O--, --O--CO--NR.sup.1--,
--NR.sup.1--CO--NR.sup.1--, --CH.dbd.CH--, --C--C--, --O--CO--O--
and -Si(CH.sub.3).sub.2--O--Si(CH.sub.3).sub.2-- [wherein R.sup.1
represents a hydrogen atom or a lower alkyl], an aromatic group, or
an alicyclic group] but any two of the oxygen atoms therein being
not directly bonded to each other);
[0045] Q represents an oxygen atom or --NR.sup.1-- [wherein R.sup.1
represents a hydrogen atom or a lower alkyl]; and
[0046] X and Y each independently represent hydrogen, fluorine,
chlorine, cyano, or an alkyl having 1 to 12 carbon atoms (and may
be substituted with fluorine, one or more out of its --CH.sub.2--
groups which are not adjacent to each other being allowed to be
substituted with --O--, --CO--O--, --O--CO-- and/or
--CH.dbd.CH--).
[0047] Of all of cinnamate and coumalin represented by the
above-mentioned formulae in the invention, compounds described in
Japanese Patent Application National Publication No. 2004-536185
are preferably used.
[0048] A monomer or oligomer having one or more functional groups,
besides the above-mentioned polymer, is added into the
above-mentioned alignment layer composition. As the monomer or
oligomer, a single selected from the following or a mixture of two
or more therefrom can be used: monofunctional monomers having an
acrylic functional group (such as reactive ethyl (meth)acrylate,
ethylhexyl (meth)acrylate, styrene, methylstylene, and
N-vinylpyrrolidone); and polyfunctional monomers having the same
(such as polymethylolpropane tri(meth)acrylate, hexanediol
(meth)acrylate, triethylene(polypropylene) glycol diacrylate,
tripropylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate, pentaerythritol tri(meth)acrylate,
dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di(meth)
acrylate, neopentyl glycol di(meth)acrylate, and isocyanuric acid
poly(meth)acrylate (such as isocyanuric acid EO diacrylate),
bisphenolfluorene derivatives (such as bisphenoxyethanolfluorene
diacrylate and bisphenolfluorene diepoxy acrylate)).
[0049] If the adhesive property between the alignment property
providing layer 12 and the refractive index anisotropic layer 13 is
sufficiently improved, the added amount of the above-mentioned
monomer(s) or the oligomer(s) can be adjusted at will as long as
the optical property of-the optical element 10 is not damaged. In
general, the weight thereof is preferably from 0.01 to 3 times
(inclusive) that of the solid content (polymer), more preferably
from 0.05 to 1.5 times (inclusive) that of the solid content for
the following reasons: if the weight thereof is not more than 0.01
time, the effect of improving the adhesive property between the
alignment property providing layer 12 and the refractive index
anisotropic layer 13 is not sufficiently expressed; on the other
hand, if the weight thereof is more than 3 times, the effect of
improving the adhesive property between the alignment property
providing layer 12 and the refractive index anisotropic layer 13 is
sufficient but sufficient alignment may not be provided to the
refractive index anisotropic layer 13. In other words, the
refractive index anisotropic layer 13 is yielded through a process
of the alignment of liquid crystal molecules and the fixation of
the alignment state thereof, as will be described later; the
above-mentioned monomer or oligomer becomes an alignment-hindering
material when the liquid crystal molecules are aligned; therefore,
a rise in the haze, the appearance of unevenness, and others based
on poorness in the alignment are caused, so that the optical
function of the liquid crystal is damaged.
[0050] The above-mentioned monomer or oligomer is preferably a
polymerizable liquid crystal material. The monomer or oligomer of
such polymerizable liquid crystal material is in particular
preferably equal in kind to the polymerizable liquid crystal
material comprised in the refractive index anisotropic layer
13.
[0051] When the transparent base material 11 is a long film and the
film is wounded into a roll form when the alignment property
providing layer 12 is laminated on the transparent base material
11, it is preferred that the kind and the added amount of the
above-mentioned monomer or oligomer are appropriately adjusted to
make the alignment property providing layer 12 into the state of a
solid analog at ambient temperature. In this case, it is preferred
to use, as the monomer or oligomer, a monomer or oligomer which is
solid at ambient temperature (20 to 25.degree. C.). According to
this, a problem of blocking, which is caused by a phenomenon that
the alignment property providing layer 12 is stuck onto the rear
face of the transparent base material 11, is not caused even if the
transparent base material 11 is wounded into a roll form when the
alignment property providing layer 12 is laminated on the substrate
11.
[0052] The refractive index anisotropic layer 13 is an optically
functional layer for realizing the function of a retardation plate,
a polarizing plate, a color filter for display, or the like, and is
a liquid crystal layer formed by curing (polymerizing) a liquid
crystal composition comprising a polymerizable liquid crystal. The
thickness of the refractive index anisotropic layer 13 is decided
in accordance with a desired optical property.
[0053] It is preferred that the liquid crystal composition for
forming the refractive index anisotropic layer 13 contains
arbitrary additives (such as a polymerization initiator, a
plasticizer, a surfactant, and a silane coupling agent), besides
one or more selected from polymerizable liquid crystal materials
which will be shown below, as long as the additives do not affect
the alignment or the optical property of the liquid crystal. The
added amount of the additives is appropriately adjusted in
accordance with the liquid crystal material in the liquid crystal
composition, or the like. In general, it is preferred that the
amount is from 0.001 to 10% by weight (inclusive) of the solid
content (polymerizable liquid crystal material). This liquid
crystal composition can be applied, as it is, onto the alignment
property providing layer 12. However, the composition may be
dissolved in an appropriate solvent such as an organic solvent in
order to match the viscosity of the composition with an applicator
used, or obtain a good alignment state.
[0054] As the polymerizable liquid crystal material comprised in
the above-mentioned liquid crystal composition, a nematic liquid
crystal compound having nematic regularity is preferably used.
Specifically, for example, the following can be appropriately used:
compounds described in JP-A Nos. 7-258638 and 2003-287623, and
Japanese Patent Application National Publication No. 10-508882.
More specifically, compounds as represented by the following
chemical formulae (1) to (10) are preferably used:
##STR00002##
[0055] However, the nematic liquid crystal compound used in the
present embodiment is not limited to the above-mentioned compounds
and may be any liquid crystal compound that has nematic liquid
crystal property and further has, at its one or more terminals, one
or more functional groups (such as ultraviolet-curable,
polymerizable groups). A mixture of two or more that are
appropriately selected from the above-mentioned nematic liquid
crystal compounds may be used.
[0056] The liquid crystal composition comprising such a nematic
liquid crystal compound is applied onto the alignment property
providing layer 12 by a method which will be described later, and
then cured (polymerized) by the radiation of ultraviolet rays or
the like. There fractive index an isotropic layer 13 which is
finally formed in this way is a liquid crystal layer as shown in
FIG. 1, in which nematic liquid crystal molecules are fixed in the
state that the molecules are aligned in parallel to the transparent
base material 11, and may be such a refractive index anisotropic
layer 13A as shown in FIG. 2, that is, a liquid crystal layer in
which nematic liquid crystal molecules are fixed in the state that
the molecules are aligned perpendicularly to the transparent base
material 11. The liquid crystal structure of the refractive index
anisotropic layer 13 shown in FIG. 1 is a homogeneous structure
(parallel alignment structure), and this structure can give an
optically functional layer called an "A plate". On the other hand,
the liquid crystal structure of the refractive index anisotropic
layer 13A shown in FIG. 2 is a homeotropic structure (perpendicular
alignment structure). This structure can give an optically
functional layer called a "positive (+) C plate".
[0057] As the polymerizable liquid crystal material comprised in
the liquid crystal composition, a mixture of a polymerizable
nematic liquid crystal compound as described above and a chiral
agent may be used (see JP-A No. 2003-287623). The chiral agent is
used in order to induce a helical structure to nematic regularity
expressed by the nematic liquid crystal compound. As long as this
purpose is attained, the chiral agent may be any chiral agent that
is compatible with the nematic liquid crystal compound in a
solution state or a melted state and can induce a desired helical
structure to the nematic liquid crystal compound without damaging
the liquid crystal property of this liquid crystal compound.
Specifically, it is preferred to use a low molecular compound
having, in the molecule thereof, axial asymmetry, as represented by
the following general formula (11), (12) or (13):
##STR00003## ##STR00004##
[0058] In the general formula (11) or (12), R.sup.4represents
hydrogen or a methyl group. Y represents any one of the
above-mentioned formulae (i) to (xxiv). Any one of the formulae
(i), (ii), (iii), (v) and (vii) is particularly preferred. Symbols
c and d, which each represents the chain length of the alkylene
group, may be each an integer ranging from 2 to 12, preferably from
4 to 10, and more preferably from 6 to 9. The compound represented
by the formula (11) or (12) in which c or d is 0 or 1 is
insufficient in stability and is easily hydrolyzed. The compound is
also high in crystallinity. On the other hand, the compound in
which c or d is 13 or more has a low melting point (Tm). These
compounds are low in compatibility with the polymerizable liquid
crystal material having nematic regularity. Thus, phase separation
may be caused in accordance with the concentration thereof. It is
particularly unnecessary that such a chiral agent has
polymerizability. However, when the chiral agent has
polymerizability, the agent is polymerized together with the
polymerizable liquid crystal material having nematic regularity so
that cholesteric regularity is stably fixed. Accordingly, this case
is very preferable from the viewpoint of thermal stability or
others. In order to obtain the refractive index anisotropic layer
13 having good heat resistance, it is particularly preferred that
the chiral agent has polymerizable functional groups at both
terminals of the molecule thereof.
[0059] In this case, a refractive index anisotropic layer which is
finally formed on the alignment property providing layer 12 is such
a refractive index anisotropic layer 13B as shown in FIG. 3, that
is, a liquid crystal layer in which nematic liquid crystal
molecules are fixed in a helical structure state that the molecules
are planar-aligned to the transparent base material 11 (a state
having cholesteric regularity) In this case, the liquid crystal
structure of the refractive index anisotropic layer 13B becomes a
cholesteric structure. This structure can give an optically
functional layer called a "negative (-) C plate".
[0060] The refractive index anisotropic layer which is finally
formed on the alignment property providing layer 12 may be such a
refractive index anisotropic layer 13C as shown in FIG. 4, that is,
a layer in which the refractive index anisotropic layer 13 shown in
FIG. 1 and the refractive index anisotropic layer 13B shown in FIG.
4 are laminated onto each other. Besides this, a layer in which two
or more layers of the same kind or different kinds out of the
liquid crystal layers 13, 13A and 13B shown in FIGS. 1, 2 and 3 are
laminated onto each other may be used.
[0061] As shown in FIG. 5, a barrier layer (intermediate layer) 14
may be formed between the alignment property providing layer 12 and
the refractive index anisotropic layer 13 in order to block the
elution of the plasticizer and so on contained in the transparent
base material 11 and the others. Examples of the material of the
barrier layer 14 include ultraviolet curable acrylic urethane
resin, ultraviolet curable polyester acrylate resin, ultraviolet
curable epoxy acrylate resin, ultraviolet curable polyol acrylate
resin, and ultraviolet curable epoxy resin. In general, the
ultraviolet curable acrylic urethane resin can easily be obtained
by causing a polyester polyol to react with an isocyanate monomer
or prepolymer to yield a product, and then causing the product to
react with an acrylate monomer having a hydroxy group, such as
2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate
(hereinafter, the term "acrylate" includes the meaning of
"methaerylate" as well as that of "acrylate"), or 2-hydroxypropyl
acrylate. In general, the ultraviolet curable polyester acrylate
resin can easily be obtained by causing a polyol (such as polyester
polyol) to react with 2-hydroxyethylacrylate or a 2-hydroxyacrylate
based monomer. A specific example of the ultraviolet curable epoxy
acrylic resin is a product obtained by preparing an oligomer of
epoxyacrylate, adding a reactive diluting agent and a photoreaction
initiator to this oligomer, and then causing the oligomer to react.
Examples of this photoreaction initiator include benzoin
derivatives, oxime ketone derivatives,benzophenone derivatives, and
thioxanthone derivatives. One or more selected therefrom maybe
used. Specific examples of the ultraviolet curable polyol acrylate
resin include trimethylolpropane triacrylate, ditrimethylolpropane
tetraacrylate, pentaerythritol triacrylate, pentaerythritol
tetraacrylate, dipentaerythritol hexaacrylate, alkyl-modified
dipentaerythritol pentaacrylate, bis(acryloxyethyl)isocyanurate,
and tri (acryloxyethyl) isocyanurate. These resins are usually used
together with a known photosensitizer.
[0062] When an improvement in the adhesive property between the
barrier layer 14 and the alignment property providing layer 12 is
considered, it is preferred to add, as the material of the barrier
layer 14, a monomer or oligomer that is equal in kind to the
monomer or oligomer having one or more functional groups and is
added to the alignment layer composition for forming the alignment
property providing layer 12. According to this, the monomer or
oligomer contained in the barrier layer 14 is crosslinked with
molecules in the alignment property providing layer 12 adjacent to
the barrier layer 14, whereby the adhesive property between the
barrier layer 14 and the alignment property providing layer 12 can
be improved in the same manner as in the above-mentioned case (the
case that the adhesive property between the alignment property
providing layer 12 and the refractive index anisotropic layer 13 is
improved).
[0063] Instead of the barrier layer 14, an intermediate layer such
as an adhesive layer may be formed in order to improve the adhesive
property between the transparent base material 11 and the alignment
property providing layer 12.
[0064] The following will describe a method for manufacturing the
optical element 10 having such a structure with reference to FIGS.
6A to 6G.
[0065] For example, a transparent resin film is first prepared as a
transparent base material 11 (FIG. 6A). Next, a barrier layer 14 is
formed on one of the surfaces of this transparent base material 11
(FIG. 6B).
[0066] When, for example, an ultraviolet curable resin is used as
the material of the barrier layer 14 formed on the transparent base
material 11, the composition for the barrier layer is applied
thereto and then cured (polymerized) by the irradiation thereof
with ultraviolet rays or the like.
[0067] Next, an alignment layer composition comprising a polymer
and a monomer or oligomer having one or more functional groups
(and, preferably, a coupling agent) is applied onto the barrier
layer 14 formed on the transparent base material 11, so as to form
a coating film 12' made of the alignment layer composition (FIG.
6C). At this time, the alignment layer composition is dissolved
into an organic solvent, and the resultant solution of the
alignment layer composition is applied. Examples of the methodused
for the application include spin coating, bar coating, extrusion
coating, direct gravure coating, reverse gravure coating, and die
coating. However, the method is not limited thereto.
[0068] Thereafter, the coating film 12' made of the alignment layer
composition and formed on the barrier layer 14 in this way is
subjected to heating and drying treatment, and then the added
monomer or oligomer is cured while the absorption wavelengths of
the alignment layer composition are cut. Thereafter, the resultant
is subjected to treatment of radiating ultraviolet rays L1 in an
arbitrary polarized light state, rubbing treatment or some other
treatment. In this way, alignment limiting force is expressed on
the surface of the coating film 12' of the alignment layer
composition. Thus, an alignment property providing layer 12 is
formed as an alignment layer (FIG. 6D).
[0069] Next, a liquid crystal composition comprising a
polymerizable liquid crystal material is applied onto the alignment
property providing layer 12 formed on the barrier layer 14 in this
way, so as to form a coating film 13' made of the liquid crystal
composition (FIG. 6E). At this time, the liquid crystal composition
is dissolved into an organic solvent, and the resultant liquid
crystal composition solution is applied. Examples of the method
used for the application include spin coating, bar coating,
extrusion coating, direct gravure coating, reverse gravure coating,
and die coating. However, the method is not limited thereto.
[0070] Thereafter, heat H is applied to the coating film 13' made
of the liquid crystal composition and formed on the alignment
property providing layer 12 in this way, thereby subjecting the
film 13' to heating and drying treatment. The alignment direction
of the liquid crystal molecules in the coating film 13' of the
liquid crystal composition is regulated by the alignment limiting
force expressed on the alignment property providing layer 12
surface. In this way, a coating film 13'' of the liquid crystal
composition to which alignment property is provided is formed (FIG.
6F).
[0071] In a nitrogen atmosphere, ultraviolet rays L2 are radiated
as energy radiation onto the coating film 13'' of the liquid
crystal composition to which the alignment property is provided in
this way, thereby curing the coating film 13'' of the liquid
crystal composition to fix the alignment state of the liquid
crystal molecules. In this way, a refractive index anisotropic
layer 13, which is a liquid crystal layer in which the alignment
state of the liquid crystal molecules is fixed, is formed on the
alignment property providing layer 12 (FIG. 6G)). The ultraviolet
rays L2 are preferably rays containing wavelengths ranging from 100
to 450 nm, more preferably rays containing wavelengths ranging from
250 to 400 nm. The rays having wavelengths within this range can
easily be obtained from an ordinary light source. When a
polymerization initiator which is widely commercially available is
used, a chemical reaction, such as ultraviolet curing reaction, can
be more easily and effectively attained. The energy radiation used
to cure the coating film 13'' of the liquid crystal composition may
be any energy radiation which is capable of curing the
above-mentioned polymerizable liquid crystal material. Besides the
ultraviolet rays, an electron beam, visible rays, infrared rays or
the like can be appropriately used in accordance with conditions.
However, the ultraviolet rays are preferred from the viewpoint of
easiness of the process therefor or the like.
[0072] As described above, according to the present embodiment, the
monomer or oligomer having has one or more functional groups is
added to the alignment layer composition for forming the alignment
property providing layer 12 for providing alignment property to the
refractive index anisotropic layer 13; therefore, the structure of
the alignment property providing layer 12 made of the alignment
layer composition becomes a strong network structure so that the
strength of the alignment property providing layer 12 itself can be
improved. Moreover, the monomer or oligomer in the alignment
property providing layer 12 is crosslinked with the molecules in
the refractive index anisotropic layer 13, which is adjacent to the
alignment property providing layer 12, near the interface between
the alignment property providing layer 12 and refractive index
anisotropic layer 13; therefore, the adhesive property between the
alignment property providing layer 12 and the refractive index
anisotropic layer 13 can be improved. As a result, the
finally-produced optical element 10 is excellent in the adhesive
property between the alignment property providing layer 12 and the
refractive index anisotropic layer 13, and further the endurance of
each of the layers therein is also excellent. It is therefore
possible to solve effectively problems that the refractive index
anisotropic layer 13 is peeled and further a rise in the haze, the
appearance of unevenness, and others are caused on the basis of
poorness in the alignment thereof.
[0073] Furthermore, when the-monomer or oligomer added to the
alignment layer composition is a polymerizable liquid crystal
material and further this polymerizable liquid crystal material is
equal in kind to the polymerizable liquid crystal material
comprised in the refractive index anisotropic layer 13, the monomer
or oligomer in the alignment property providing layer 12 is more
easily crosslinked with the molecules in the refractive index
anisotropic layer 13, which is adjacent to the alignment property
providing layer 12. As a result, the adhesive property between the
alignment property providing layer 12 and the refractive index
anisotropic layer 13 can be further improved according to the
present embodiment.
EXAMPLES
[0074] The following will describe specific examples of the
above-mentioned embodiments.
Example 1
[0075] Cyclohexanone (98 parts by weight) was added to an alignment
layer composition containing a polymer having a cinnamoyl group
(1.0 part by weight) and the polymerizable nematic liquid crystal
compound monomer represented by the chemical formula (1) (1.0 part
by weight), and the composition was dissolved therein to yield a
solution of the alignment layer composition. A pentaerythritol
acrylate (PETA) monomer was applied onto a long triacetylcellulose
(TAC) film (thickness: 80 .mu.m), and then irradiated with
ultraviolet rays, so as to be cured, thereby forming a barrier
layer of 7 .mu.m thickness on the TAC film. The solution yielded as
described above was applied onto the barrier layer formed on the
TAC film with a wire bar coater, and then the resultant layer was
dried with hot wind of 80.degree. C. temperature for 2 minutes, so
as to yield a coating film of 0.1 .mu.m thickness. This coating
film was irradiated with polarized ultraviolet rays at 10
mJ/cm.sup.2 to form an alignment layer in which alignment limiting
force was expressed on its surface.
[0076] Next, a liquid crystal composition containing the same
polymerizable nematic liquid crystal compound monomer as added to
the alignment layer composition solution was dissolved into a
solution of toluene at a ratio of 20% by mass. Furthermore, thereto
was added a polymerization initiator (IRGACURE-907 (trade name),
manufactured by Chiba Speciality Chemicals) to yield a solution of
the liquid crystal composition. This solution was applied onto the
alignment layer formed in the above-mentioned step with a wire bar
coater, and the resultant was dried to yield a coating film of 1
.mu.m thickness. Next, this coating film was heated at 85.degree.
C. for 2 minutes to align the liquid crystal molecules in the
coating film by the alignment limiting force expressed on the
surface of the alignment layer. Thereafter, a high-pressure mercury
lamp was used to radiate ultraviolet rays at 100 mJ/cm.sup.2 onto
the coating film in a nitrogen atmosphere, thereby curing the
coating film together with the alignment layer to fix the alignment
state of the liquid crystal molecules. In this way, a nematic
liquid crystal layer was formed on the alignment layer, so that an
optical element according to Example 1 was finally produced.
Example 2
[0077] A nematic liquid crystal layer was formed on an alignment
layer to manufacture an optical element according to Example 2
finally in the same way as in Example 1 except that the
polymerizable nematic liquid crystal compound monomer added to the
alignment layer composition therein was changed to isocyanuric acid
EO modified diacrylate.
Example 3
[0078] n-Methylpyrrolidone (98 parts by weight) was first added to
an alignment layer composition comprising polyimide (1.0 part by
weight) and the polymerizable nematic liquid crystal compound
monomer represented by the chemical formula (1) (1.0 part by
weight), and the composition was dissolved therein to yield a
solution of the alignment layer composition. A pentaerythritol
acrylate (PETA) monomer was applied onto a long triacetylcellulose
(TAC) film (thickness: 80 .mu.m), and then irradiated with
ultraviolet rays, so as to be cured, thereby forming a barrier
layer of 7 .mu.m thickness on the TAC film. The solution yielded as
described above was applied onto the barrier layer formed on the
TAC film with a spin coater, and then the resultant layer was dried
with hot wind of 100.degree. C. temperature for 1 minute, so as to
yield a coating film of 1 .mu.m thickness. This coating film was
subjected to rubbing treatment to form an alignment layer in which
alignment limiting force was expressed on its surface.
[0079] Next, a nematic liquid crystal layer was formed onto the
alignment layer formed as described above in the same way as in
Example 1, so as to manufacture an optical element according to
Example 3 finally.
Example 4
[0080] An alignment layer was first formed on a triacetylcellulose
(TAC) film having a barrier layer in the same way as in Example
1.
[0081] Next, a liquid crystal composition comprising the same
polymerizable nematic liquid crystal compound monomer as added to
the alignment layer composition was dissolved into a toluene
solution to give a ratio of 20% by mass. Furthermore, thereto were
added a chiral agent (the compound represented by the chemical
formula (2)) and a polymerization initiator (IRGACURE-907 (trade
name), manufactured by Chiba Speciality Chemicals), so as to yield
a liquid crystal composition solution. This solution was applied
onto the alignment layer formed in the above-mentioned step with a
wire bar coater, and the resultant layer-was dried to yield a
coating film of 1 .mu.m thickness. Next, this coating film
was-heated at 85.degree. C. for 2 minutes to align the liquid
crystal molecules in the coating film by the alignment limiting
force expressed on the surface of the alignment layer. Thereafter,
a high-pressure mercury lamp was used to radiate ultraviolet rays
onto the resultant at 100 mJ in a nitrogen atmosphere, thereby
curing the coating film together with the alignment layer to fix
the alignment state of the liquid crystal molecules. In this way, a
cholesteric liquid crystal layer was formed on the alignment layer
to manufacture an optical element according to Example 4
finally.
Comparative Example
[0082] Cyclohexanone (98 parts by weight) was added to an alignment
layer composition containing a polymer having a cinnamoyl group
(2.0 parts by weight) and the composition was dissolved therein to
yield a solution of the alignment layer composition. In the same
way as in Example 1, this solution was applied onto a barrier layer
formed on a long triacetylcellulose (TAC) film (thickness: 80
.mu.m) with a wire bar coater, and then the resultant layer was
dried with hot wind of 80.degree. C. temperature for 2 minutes, so
as to yield a coating film of 0.1 .mu.m thickness. This coating
film was irradiated with polarized ultraviolet rays at 10
mJ/cm.sup.2 to form an alignment layer in which alignment limiting
force was expressed on its surface.
[0083] Next, a liquid crystal composition comprising the
polymerizable nematic liquid crystal compound monomer represented
by the chemical formula (1) was dissolved into a toluene solution
to give a ratio of 20% by mass. Furthermore, thereto was added a
polymerization initiator (IRGACURE-90 (trade name), manufactured by
Chiba Speciality Chemicals), so as to yield a liquid crystal
composition solution. This solution was applied onto the alignment
layer formed in the above-mentioned step with a wire bar coater,
and the resultant layer was dried to yield a coating film of 1
.mu.m thickness. Next, this coating film was heated at 85.degree.
C. for 2 minutes to align the liquid crystal molecules in the
coating film by the alignment limiting force expressed on the
surface of the alignment layer. Thereafter, a high-pressure mercury
lamp was used to radiate ultraviolet rays onto the resultant at 100
mJ in a nitrogen atmosphere, thereby curing the coating film
together with the alignment layer to fix the alignment state of the
liquid crystal molecules. In this way, a nematic liquid crystal
layer was formed on the alignment layer to manufacture an optical
element according to Comparative Example finally.
(Evaluation Results)
[0084] About each of the optical elements according to Examples 1
to 4 and Comparative Example, a lattice pattern cutting test was
made according to JIS 5400 in order to evaluate the adhesive
property thereof. Specifically, a Sellotape (registered trade mark)
(CT 24, manufactured by NICHIBAN CO., LTD.) was caused to adhere
onto the film with the finger cushion, and subsequently the tape
was peeled. The evaluation was made on the basis of the number of
squares in which the tape was not peeled out of 100 squares in the
lattice pattern. A case in which the liquid crystal layer was not
peeled at all was expressed as 100/100. A case in which the liquid
crystal layer was completely peeled was expressed as 0/100. The
results are shown in Table 1 described below. As is evident form
Table 1, the optical elements according to Examples 1 to 4 had good
adhesive property but the optical element according to Comparative
Example had poor adhesive property.
[0085] Next, about each of the optical elements according to
Examples 1 to 4 and Comparative Example, the haze value thereof was
measured with a haze meter (manufactured by Nippon Denshoku
Industries Co., Ltd.) in order to evaluate the alignment property
of the liquid crystal layer thereof. A case where the haze value
was 0.3% or more was judged to be good, and a case where the haze
value was less than 0.3% was judged to be poor. The results are
shown in Table 1. As is evident from Table 1, in each of Examples 1
to 4 and Comparative Example, the alignment state of the liquid
crystal molecules was even.
TABLE-US-00001 TABLE 1 Peeling test Alignment Examples 1 100/100
.largecircle. 2 100/100 .largecircle. 3 100/100 .largecircle. 4
100/100 .largecircle. Comparative 1 0/100 .largecircle. Example
* * * * *